Alexander Zverev claimed his first victory as world number one as he swept aside Rafael Jodar in the opening match of the ATP Finals.
Germany's Zverev produced a serving masterclass to beat the fast-rising Spaniard 6-4 6-4.
The French and US Open champion dropped only 10 points on serve, landing an astonishing 84% of first serves and hitting 10 aces.
The only time Zverev looked troubled was when he went two break points down as he served for the opening set - before saving them with back-to-back aces.
"I still think I have a lot of things to improve. It was not a perfect match but to start the tournament, I am very happy," the 29-year-old said.
"Winning always helps, but it's been a good match."
Zverev lost his first match as world number one at the Paris Masters in November and said afterwards he was "annoyed" at the reaction to his rise to the top of the rankings.
He has taken full advantage of a year in which Carlos Alcaraz and Jannik Sinner have struggled with injuries, winning two majors and reaching the Wimbledon final.
Zverev underlined his status as the world's best player by walking out on court in Turin in a custom black leather jacket with a number one printed on the back.
